Inborn errors of metabolisms resulting in hyperammonemia or other endogenous neurologic toxins

Exogenous toxin ingestions that are amenable to dialytic removal:

Low protein binding

Molecular weight less than 15-30 kilodaltons

Low volume of distribution

Key management points

Pediatric renal replacement therapy for acute kidney injury has become more commonplace over the past two decades. Three modalities are available and should be individualized for each patient and their clinical situation.

Intermittent hemodialysis is usually most appropriate for patients who are hemodynamically stable and larger than 10 kg.

Peritoneal dialysis is usually most appropriate for patients who are hemodynamically stable, smaller than 10 kg, who have not had major abdominal surgery and infants after congenital heart surgery.

Continuous renal replacement therapy is usually most appropriate for patients who are hemodynamically unstable and of any size.

2. Emergency Management

The emergency management indications for initiating acute renal replacement therapy in children include immediate life-threatening, or severe complications of acute kidney injury that are refractory to medical/pharmacological therapy:

3. Diagnosis

The diagnosis for renal replacement therapy requirement in children with acute kidney injury requires a complex clinical and laboratory assessment of the patient’s current status, ongoing needs and predicted future course. There is no hard and fast rule for initiating renal replacement therapy.

Current status assessment

If the patient has any of the following, then an assessment of ongoing needs and predicted future course must be undertaken to determine if renal replacement therapy should be initiated.

The normal serum electrolyte and creatinine ranges vary by pediatric age as a function of tubular maturation and increase in muscle mass during growth and development. The following table lists the general ranges based on patient age. These values should serve only as one piece of data to inform clinical decision making as many electrolyte concentrations can be affected by dietary and other non-kidney function related factors.

Ongoing needs assessment

An assessment of the patient’s fluid and associated electrolyte needs should be made at least daily. If the volume and solute load required for the day would likely lead to worsening clinical status from the sequelae of acute kidney injury, then assessment of the patient’s predicted future course must be undertaken to determine if renal replacement therapy should be initiated.

Fluid volume needed:

Nutrition (TPN + enteral feeds)

Medication volumes

Blood product requirements

Solute burden:

Nutrition (TPN + enteral feeds)

Medications (sodium is prevalent in many antibiotics)

Blood products (sodium and potassium are present in blood products)

Predicted future course

A realistic assessment of the patient’s resolution of acute kidney injury with resumption of adequate urine output and electrolyte homeostasis must be undertaken at least daily.

If the patient already has signs and symptoms of the sequelae of acute kidney injury with volume overload and electrolyte imbalance, and/or if the daily ongoing needs to for nutrition/blood products/medication would put the patient a risk for worsening sequelae, and the kidney function is not expected to improve in the next 24 hours, renal replacement therapy initiation should be strongly considered.

The clinical criteria to diagnose when a patient needs renal replacement therapy is guided by the principles discussed in the previous section. In addition, recent pediatric data suggest patients with acute kidney injury and a relative intensive care unit fluid accumulation of > 10-20% of their intensive care unit admission body weight are at increased risk for mortality.

Epidemiology

Pediatric patients receiving acute renal replacement therapy do so as a result of another system illness or its treatment and not primary kidney disease

Continuous renal replacement therapy has become the most common modality to support children with acute kidney injury, with the exception that continuous peritoneal dialysis is preferred in smaller children less than 8 kg

CRRT has proven effective across the span of pediatric age range (0-25 years) and sizes (2-200kg), but requires special technical expertise in small children.

Prognosis

The prognosis for children receiving acute renal replacement therapy is related to a number of clinical and demographic variables

Patient characteristics

Children receiving CRRT less than 1 year of age or 10 kg have a lower survival rate than older/larger patients (43% vs 63%)

Children receiving CRRT with another major system illness have lower survival than patients with less complex disease:

Liver transplant/disease – 31%

Bone marrow transplant – 45%

Pulmonary disease/transplant – 45%

Malignancy – 48%

Cardiac disease/transplant – 51%

Sepsis – 59%

Shock – 68%

Renal disease – 84%

Clinical variables

Multiple single- and multi-center studies show that ICU fluid accumulation at CRRT initiation is independently associated with increased risk of mortality, although to date, no randomized trial as assessed the impact of fluid accumulation on outcome